The invention relates to a seam-weaving machine for making a plastics woven fabric endless by means of a woven seam. To form the weaving shed, the seam-weaving machine has a Jacquard machine, this being arranged underneath the weaving shed and the harness cords being drawn back by tension springs secured above the weaving shed.
Industrial plastics woven fabrics for uses in which a regular surface structure of the woven fabric is required, especially flat-woven paper-forming fabrics made from plastics mono-filaments, are made endless by a woven seam. To produce a woven seam, the warp threads are exposed to a length of e.g. 15 cm at the woven fabric ends which are to be joined to each other, the weft threads in this zone being removed. The woven seam, in which the original weave binding is exactly reproduced, is then formed from these warp thread fringes and the weft threads removed from a cut-off piece of woven fabric. An auxiliary weaving shed or seam-weaving shed is spread out from the removed weft threads, in which the removed weft threads function as auxiliary warp threads. The warp thread fringes projecting from the one woven fabric end and from the other woven fabric end are then inserted alternately into this seam-weaving shed as auxiliary weft threads.
The warp thread fringes, aligning with each other, of the one woven fabric end and of the other woven fabric end are in each case woven in only up to the so-called splice point, at which they are then guided out of the woven fabric and later cut off. The splice points are offset within the woven seam according to a specific pattern, which is of great significance for the tensile strength and quality of the woven seam. Jacquard machines are therefore particularly suitable for the formation of a seam-weaving shed with programmed splice points and the use of a Jacquard machine to produce a woven seam in known from U.S. Pat. No. 4,410,015 granted Oct. 18, 1983. The Jacquard machine is arranged in the usual manner above the seam-weaving shed, so that the harness cords emerging on the underside of the Jacquard machine can be guided on a straight path through the seam-weaving shed. The harness cords are drawn downwards by weights secured to the harness cords underneath the seam-weaving shed.
As is known from DE-C-704 153, the overall height of a weaving machine can be reduced by so designing the Jacquard machine that the harness cords are guided out at the upper side and then arranging the Jacquard machine underneath the weaving shed. Secured above the weaving shed is a tension spring grille in which are suspended tension springs which draws the harness cords back upwards. The use of return springs instead of weights also has the advantage that the operating speed of the Jacquard machine can be increased. Such an upside-down arrangement of a Jacquard machine in the manufacture of a woven seam for the production of a continuous paper-forming fabric is known from U.S. Pat. No. 4,581,794 granted Apr. 15, 1986. This type of arrangement of a Jacquard machine is also generally known in belt-weaving machines. However, these are special cases. As a rule, Jacquard machines are still arranged above the weaving shed.